Constraints on Dark Matter from Dynamical Heating of Stars in Ultrafaint Dwarfs. Part 2: Substructure and the Primordial Power Spectrum

TL;DR

This paper introduces a novel method to constrain small-scale dark matter structures and the primordial power spectrum by analyzing the heating effects on stars in ultra-faint dwarf galaxies, surpassing previous bounds.

Contribution

It presents a new observational approach to probe dark matter substructures and primordial fluctuations at scales previously inaccessible, providing stronger constraints on dark matter models and inflation.

Findings

Constraints on the primordial power spectrum are orders of magnitude stronger for certain scales.

The method sets new limits on dark matter isocurvature perturbations.

Many dark matter models with dense structures can be constrained using this approach.

Abstract

There is a large and growing interest in observations of small-scale structure in dark matter. We propose a new way to probe dark matter structures in the $\sim 10 - 10^8 \, M_\odot$ range. This allows us to constrain the primordial power spectrum over shorter distances scales than possible with direct observations from the CMB. For $k$ in the range $\sim 10 - 1000 \, {\rm Mpc}^{-1}$ our constraints on the power spectrum are orders of magnitude stronger than previous bounds. We also set some of the strongest constraints on dark matter isocurvature perturbations. Our method relies on the heating effect such dark matter substructures would have on the distribution of stars in an ultra-faint dwarf galaxy. Many models of inflation produce enhanced power at these short distance scales and can thus be constrained by our observation. Further, many dark matter models such as axion dark matter, self-interacting dark matter and dissipative dark matter, produce dense structures which could be constrained this way.